The Justice Department sent Mexico a provisional arrest warrant for the drug lord, Rafael Caro Quintero, as a prelude to an extradition request. The officials, who asked not to be identified discussing the confidential collaboration, said Mexico’s attorney general privately encouraged the United States to send the request, a sign that the government there would act on it.

The case has stirred strong feelings among American law enforcement officials and become a fresh test of the relationship between the two neighboring countries at a time when they are trying to broaden it beyond the issues of crime, drugs and immigration. Vice President Joseph R. Biden Jr. plans to visit Mexico next month to talk about ways to expand economic ties, and both governments appear eager to avoid any enduring damage over the release of Mr. Caro Quintero.

Brian Fallon, a Justice Department spokesman, said that he could not comment on any arrest request but that Attorney General Eric H. Holder Jr. had personally involved himself in discussions. “The attorney general is in contact with top Mexican authorities to convey concerns about the release and figure out steps forward,” Mr. Fallon said.

The American authorities are also searching for other ways to go after Mr. Caro Quintero, who was convicted in the murder of Enrique Camarena, a Drug Enforcement Administration agent known as Kiki, who was abducted, tortured and killed in 1985. The Treasury Department is examining whether it can squeeze Mr. Caro Quintero financially while the Justice Department prepares an Interpol arrest request.

Mexico’s attorney general, Jesús Murillo Karam, has expressed concern about the decision by a Mexican court to release Mr. Caro Quintero, who had served 28 years of a 40-year sentence, and said he would appeal the ruling to the country’s Supreme Court. He told United States authorities on Monday that they should file their arrest request, and lawyers worked overnight to draft it, according to an American official. A Mexican official said that Mr. Murillo Karam encouraged the American arrest request in case he was unsuccessful in reversing the ruling in a Mexican court.

Whether Mexican authorities can find Mr. Caro Quintero again remains an open question. When he was released from prison in Jalisco State at 2 a.m. Friday, security agents monitoring the facility decided to follow him, but they lost him, the Mexican official said. The official said security agents now have an idea about his whereabouts and are looking into that.

American and Mexican officials have said they were caught off guard by the court’s ruling, with legal experts saying that Mr. Caro Quintero’s lawyers outflanked prosecutors with a technical, but often successful, argument that the case was improperly prosecuted in federal court rather than state court.

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Rafael Caro QuinteroCreditAgence France-Presse — Getty Images

Mexico’s foreign minister, José Antonio Meade, reiterated Mexico’s disagreement with the decision and said it would work to ensure “it is corrected,” but he sidestepped questions about whether the United States had filed an extradition request. Foreign Ministry officials declined to comment.

Mexican legal experts said Mr. Caro Quintero could not be extradited for Mr. Camarena’s killing because of a double jeopardy provision in the extradition treaty that bars turning anyone over on a charge that has been heard in trial. American lawyers could argue that the judge’s ruling effectively meant that he never was legitimately tried and that double jeopardy does not apply.

The United States could also seek his extradition on other crimes he is suspected of committing. The government has long maintained that Mr. Caro Quintero continued his ties to an extensive drug and money-laundering network even from prison, and in June the Treasury Department leveled sanctions against 18 people, including six members of his family, and 15 businesses or other entities tied to him.

If the United States found a crime for which Mr. Caro Quintero had not been prosecuted, it would have to fall within the statute of limitations in Mexico, and the United States would have to assure that he would not face the death penalty, a condition that Mexico has insisted on in the past because it does not have capital punishment, said José Antonio Caballero, a law professor at the university known as CIDE who has reviewed the Caro Quintero case.

Mr. Caro Quintero was indicted by a federal grand jury in Los Angeles in January 1988, accused of masterminding the killing of Mr. Camarena to protect his drug-trafficking organization, which was smuggling marijuana and cocaine into the United States.

In January 1989, Mr. Caro Quintero and another man were convicted in Mexico of killing Mr. Camarena and two other Americans, John Walker and Alberto Radelat, who were living in Mexico and whom his henchmen had mistaken for D.E.A. agents.

At the time, Mexico rarely extradited its citizens to face trial abroad, but under President Felipe Calderón, who forged close ties with the United States on fighting drug crime, extraditions of major cartel figures soared. During President Enrique Peña Nieto’s eight months in office, the pace has slowed considerably; the Justice Department has not released a tally.

American officials are worried that the second man convicted in the Camarena case, Ernesto Fonseca Carrillo, may also be freed under the legal tactic. If the federal court did not have jurisdiction in the killing, then Mr. Fonseca Carrillo’s conviction might also be moot.

Although Mr. Caro Quintero also faced state charges, the court decided he had already served time in prison commensurate with whatever sentence he might receive.

A version of this article appears in print on , on Page A8 of the New York edition with the headline: U.S. Asks for Arrest of Mexican Kingpin Who Was Freed in American’s Murder. Order Reprints | Today’s Paper | Subscribe